ietf-smtp
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Re: 2821bis/ter and procedures

2008-08-09 19:41:49

Richard Kay wrote:

However, as it was found, not all support this and common sense tells you it should not matter - a 45x means a retry is possible. So doing a generic faster 2nd retry for 45x responses proved to work better in all cases.

Would it be worth considering whether or not to recommend after a first 45x to
DATA, the sender splits the message up on the second attempt ?
This IMV, creates a semantic issue and enables a 45x to data to
carry additional meaning to the client - the server is saying
maybe I'm busy try later (traditional meaning) or maybe different recipients require different responses (new meaning).

Its an interesting implementation idea to consider for extreme cases where maybe its the 4th or 5th attempt or maybe even the final attempt will it will finally try a split into single transactions.

Off hand, I think the 2nd faster retry worked well enough that would not make this necessary.

Also, consider, that if any of the RCPT are remote (not local address or hosted domains), where a relay situation will be required for final delivery once the receiver accepts the message, then in the case, most systems require authentication or authorization - otherwise you have an open relay system, and the acceptance of local RCPT should not trump the authorization requirement for a remote RCPT address:

    (for non-ESMTP AUTH session)

    RCPT TO: local
    250 OK
    RCPT TO: remote
    550 Authentication/Authorization required.
    DATA
    354 ...
    451 Try again later

For us, when ESMTP AUTH occurs, the sender totally by-pass all SMTP level receiver AVS strategies, and the operator decides at the content level what happens there:

    (for ESMTP AUTH session)

    RCPT TO: local
    250 OK
    RCPT TO: remote
    250 OK
    DATA
    354 ...
    250 Message accepted

> Perhaps then if the server is
> genuinely overloaded it should not respond to the
> next helo/ehlo from the same client, and the client should back off
> increasing delays each attempt.

I believe many servers do employ connection and session loading limits. I don't think the greylist response should not have any other meaning other than what the SMTP model defines 4yz - a temporary situation - try again later.

--
Sincerely

Hector Santos, CTO
http://www.santronics.com
http://santronics.blogspot.com